Fortune Favors the Duke by Kristin Vayden

The new Duke has a proper scandal brewing.

Quinton Errington is perfectly happy teaching at Cambridge, with his elder brother carrying the duties of being the Duke of Wesley. But when a trip to celebrate Wesley’s last week of bachelorhood ends in tragedy, Quinton, who becomes the Duke, would give anything to have his brother back.
Wesley’s would-be bride, Catherine Greatheart, is left heartbroken and alone. Her grandmother has fallen ill, and Catherine has nowhere left to turn but to the family she was so close to being part of. The new Duke is kind, and she could use a friend.
Between learning how to be the head of his family, mourning his brother, and trying not to fall in love with his late-brother’s fiancée, Quinton will need some help—and it’s a good thing he’s not alone.